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My 1971 521


d.p

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Power comes off switched ignition on the fuse box and ground is on the body behind one of the brake line clamp/holders.  None of that changed as of late so something else must have.  I threw a multimeter on it (red wire > green wire going to coil and black wire to ground) and it read the same (around 9-10 volts IF I had it set right) regardless if the lights were on or not.  


I can move the power from the fuse box directly to the battery to see if that fixes it but I read somewhere that is less than ideal?  

 

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DP I have dome 3 motor pulls and n 2nd Trans already. 54yrs old Im done crawling around.I got a 92 Toyota with 77k Miles for 1500. If I daily drive that the 521 will surely last 10more years, If a daily the 521 I think maybe another 3-5 on motor trans not counting the other stuff that may go bad. Kingpins again diff ect….

 

the tach maybe a dirty ground,

 

try with just the parking lights on and see if still does that.  If anyhting I woud think it would be the opposite ,works better with lights OFF

 

where you get the positive from?????? 9-10volts is not correct. should be what the battery is and when running slightly higher 13/14volts

 

 

a lot of people just do the +12volts at the blk/white wire that when to the +side ballast resisitor as the switchable 12volts for the Tach.

 

 

Edited by banzai510(hainz)
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I cleaned the ground and re-crimped it to no avail.  Will try moving the power from the fuse box to the battery and see if it makes any difference as well as moving my ground.  Been using that power and that ground since I installed it and no issues but who the fuck knows what the problem is now.  


From my tach: 

red wire to switched ignition on the fuse box

green wire to - coil

black wire to ground on the firewall

white wire to engine bay light 

 

That's all 4 wires coming off the TACH.  

 

Its more like 11.x volts when testing with my multimeter but still no idea if I am doing it right.  k

 

Edited by d.p
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Fuck if I know. 
 

Tach doesn’t bounce in neutral and only seems to do it under load and in gear moving.  If I turn the head lights on it doesn’t jump. seems to only bounce/jump above 2500 RPMS or so.  
 

I tired going directly to the battery and it didn’t make any difference.   Moved the ground and no difference.    
 

What does turning the lights on do except drop the voltage?  Which inturn stops the tach from bouncing so too much voltage with the lights off? 
 

How do I measure voltage before and after fuses? 

C6F0395F-1013-4138-82EA-08B2659E1C95.jpeg

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Ok so driving around my little voltage cigarette meter reads 15.x and the tach bounces around. If I turn my headlights on (parking lights made no difference) then the meter drops down to 14.2 or so and the tach is fine.   
 

Could too much voltage be causing this?  If so my voltage regulator shutting the bed or my alternator? 

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Measuring the voltage before and after the fuse is exactly how it sounds.. 

With the fuse still installed Ground the negative from the meter and then check one side of the fuse compared to the opposite side.... you should have the same voltage.... I would check it at the clip that actually holds the fuse not the fuse itself..

 

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10 minutes ago, Crashtd420 said:

I would say yes... 

 

 Well cracked this mystery.
 

Replaced my “New-Era” regulator with an older 3rd party one I had prior and problem is gone.  Volts’s ready right around 14.x driving around an no epileptic tach.  
 

so assuming the new-era was shitting the bed.  Only reason I changed it out was because I assumed it was better than whatever one I had in there which is now back in.  Hehe
 

 

 

6733A643-ADB2-4218-9698-F3438F041161.jpeg

Edited by d.p
Fucking datsuns
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Just now, datzenmike said:

Original parts are always better that what you replace them with.


What?  I replaced the original voltage regulator with the black one that is in there now years ago.  Then I saw the new-era one on ebay and replaced the black one with it. Now the new-era one seems to be dying so back to the non-OEM black regulator. 

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DP you shuld have caught this and mentioned this sooner.

If that cig light meter read over 15volts its slowly cooking the batter and will ooze out and have that white shit build up.

yes most times its the External volt reg that's bad.  suppositly one can adjust the mechanical ones but never learn how to do it.

 

the solid state one VR will pop and give a OVer VOLTAGE issue. more like 16/17volts.

 

this one you have is weid as its close  15 being almost good and OK in other vehicles.

 

one way to know if VR is bad is you but on heater and lights and wiper and it still reads over 15volt then call it BAD!!!!!!!!!!

 

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